The present invention is in the field of imaging systems. More particularly, the present invention provides a method and apparatus for reducing artifacts in an imaging system by directing a stream of air onto and around the beam deflection assembly of the imaging system.
In many imaging systems, such as imagesetters or platesetters, an optical carriage is used to displace a laser system or other imaging source in a slow scan direction along an internal drum to expose a supply of recording media supported on the drum. Generally, the imaging source includes a beam deflection assembly, comprising a deflector element (e.g., a mirror) and a spin motor for rotating the deflector element, for deflecting an imaging beam generated by a radiation source across the recording media. Such an imaging system is described, for example, in U.S. Pat. No. 5,598,739, assigned to the Agfa Division, Bayer Corporation, incorporated herein by reference.
Increased speed and productivity is essential in deadline driven printing businesses, such as newspapers and the like. Accordingly, many attempts have been made to increase the imaging speed and throughput of imaging systems used by these and other businesses. One method of increasing the imaging speed involves the use of ever faster spin motors. Unfortunately, the use of faster spin motors often results in the generation of undesirable artifacts, such as banding, in the recorded image.
The present invention provides a method and apparatus for reducing artifacts in an imaging system by directing a stream of air onto the beam deflection assembly of the imaging system. In a first, preferred embodiment, the present invention provides a fan assembly oriented to direct a stream of air onto the rotating deflector element of the beam deflection assembly. The stream of air is preferably positioned to distribute a substantially uniform amount of air around the rotating deflector element. It is believed that the stream of air produced by the fan assembly reduces artifacts in the recorded image by changing the thermal gradients around the rotating deflector element, thereby cooling the rotating deflector element, and/or by maintaining a turbulent air flow around the rotating deflector element. Other air displacement systems for developing and directing a stream of air onto the rotating deflector element of the beam deflection assembly may also be used without departing from the intended scope of the present invention. Such systems may include, for example, an air compressor system for producing and directing a stream of compressed air onto the rotating deflector element.